In the related art, an optical analysis apparatus that irradiates a sample with light and analyzes a component contained in the sample using transmitted light transmitted through the sample is known. For example, in PTL 1, “A spectrometric analysis apparatus which has a function of measuring absorbance of a target sample and in which an optical system for measuring the absorbance of the sample includes a light transmitting unit in which a container storing the sample is disposed, an illumination unit including a light source for irradiating the sample stored in the container of the light transmitting unit, a photometric unit that spectrally separates transmitted light from the sample stored in the container of the light transmitting unit and detects intensity for each wavelength thereof so as to measure the absorbance of the sample, and a first optical fiber connecting the illumination unit and the light transmitting unit and guiding the illumination light, and in which partial polarization property of the illumination light of the light source is eliminated by the first optical fiber so as to cause the sample to be irradiated with the illumination light as non-polarized light” is described.